Osmotic dosage forms for delivering a drug to a fluid environment of use are known to the drug dispensing art. For example, U.S. Pat. No. 3,845,770 issued to Theeuwes and Higuchi, and in U.S. Pat. No. 3,916,899, issued to the same patentees, Theeuwes and Higuchi, an osmotic dosage form is disclosed comprising a semipermeable wall that surrounds a compartment comprising a drug. The wall is permeable to the passage of fluid and there is a passageway through the wall for delivering the drug from the dosage form. The dosage forms of these patents release the drug by fluid being imbibed through the wall into the compartment at a rate determined by the permeability of the wall and the osmotic pressure gradient across the wall to produce a solution of drug that is dispensed through the passageway from the dosage form. These dosage forms are extraordinarily effective for delivering a drug that exhibits an osmotic pressure gradient across the wall against the fluid. The dosage forms are effective also for delivering a drug mixed with an osmotically effective solute that is soluble in the fluid and exhibits an osmotic pressure gradient across the wall against an aqueous fluid.
A quantum improvement in osmotic dosage forms was presented to the medical and pharmaceutical dispensing art by inventor Theeuwes in U.S. Pat. Nos. 4,111,202; 4,111,203; and 4,203,439. In these patents, the delivery kinetics of the dosage form were enhanced for delivering a drug with varying degrees of solubility in an aqueous fluid. The kinetics are improved by manufacturing the dosage form with a drug compartment and an osmotic compartment separated by a film. These dosage forms deliver the drug by fluid being imbibed through the wall into the osmotic compartment producing a solution that causes the film to move and act as a driving force. The driving force pushes the drug through a small passageway from the dosage form.
A pioneer advancement in osmotic dosage forms was made by co-inventors Cortese and Theeuwes in U.S. Pat. No. 4,327,725 and by co-inventors Wong, Barclay, Deters and Theeuwes in U.S. Pat. No. 4,612,008. The osmotic dosage form in these patents comprise a semipermeable wall that surrounds a compartment. The compartment contains a drug formulation and an expandable hydrogel. In operation, fluid is imbibed into the compartment where it contacts the drug formulation; thereby forming a dispensable formulation that is pushed by the expanding hydrogel from the dosage form.
A further and unexpected contribution to the drug dispensing art was provided by co-inventors Deters, Theeuwes, Mullins and Eckenhoff in U.S. Pat. No. 4,627,850. In this patent, the inventors provided an osmotic capsule comprising a wall capsulating and containing a drug formulation. The drug formulation is delivered through a very small orifice manufactured without any expressed ratio to the dimensions of the osmotic capsule. The osmotic capsule of this patent delivers an effective dose of drug over time.
The osmotic dosage forms described in the above patents operate successfully for their intended use and they deliver many difficult to deliver drugs for their intended therapeutic effects. Now, it has been observed, while these dosage forms are very effective and provide many advantages for delivering drugs for their intended therapy, there are short comings associated with these dosage forms. In one manufacture, for example, these prior art dosage forms often embrace a conventional tablet shape that inherently retains or entraps drug in the inner top surface or within inner corners of the dosage form. In another manufacture, for example, the prior art dosage form embraces a conventional capsule shape comprising an inner configuration that entraps drug or restricts the flow of drug from the capsule in the immediate interior region adjacent to the orifice of the capsule; and in another instance, the drug is not delivered immediately and was delayed for hours before delivery of the drug.
It will be appreciated by those versed in the art in the light of the above presentation, that if an osmotic dosage form is provided that is essentially-free of the short comings known to the prior art, such an osmotic dosage form that would have a positive practical valve and it would also represent an advancement in the drug delivery art. The present invention advances the state of the drug delivery art by providing a novel and unique dosage form manufactured as an osmotic caplet for optimizing therapy by delivering essentially the full dose of drug present in the osmotic caplet. The osmotic caplet administers the drug at a programmed and controlled rate per unit time over a prolonged period of time. The osmotic caplet provides continuous control over the administration of the drug, and the osmotic caplet maintains this control over an extended period of time.